Aviat Space Envir Md
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Aviat Space Envir Md · Jul 2012
ReviewDifferences in cardio-ventilatory responses to hypobaric and normobaric hypoxia: a review.
The presence of differences in physiological response to a lowered inspired Po2 mediated by hypobaric hypoxia (HH) or normobaric hypoxia (NH) is controversial. This review examines the brief, acute, and subacute respiratory, cardiovascular, and subjective symptom response to intermediate and severe hypoxic exposure in NH and HH. ⋯ Explanations for the discrepancy between the two modalities include differences in ventilatory patterns, alveolar gas disequilibrium, and dissimilar acute hypoxic ventilatory responses. Awareness and consideration of these key differences between NH and HH is essential to their proper application to kinesiology, altitude, and aviation medicine.
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Aviat Space Envir Md · Apr 2010
ReviewExpansion of postoperative pneumothorax and pneumomediastinum: determining when it is safe to fly.
The possibility of expansion of pneumothorax (PTX) and/or pneumomediastinum (PMED) during commercial flights makes air travel after thoracic surgery particularly worrisome. Guidelines from the Aerospace Medical Association (AsMA) suggest delaying air travel 2 to 3 wk following uncomplicated thoracic surgery and 1 wk following radiographic resolution of PTX; they also state that PTX is an "absolute contraindication" to air travel. However, both AsMA guidelines and thoracic surgeons' recommendations for postoperative air travel require further examination. ⋯ A wide variability exists among thoracic surgeons regarding their recommendations for air travel by patients with postoperative PTX and/or PMED. Both AsMA guidelines and surgeons' recommendations should rely more on scientific evidence. Studies of PTX and PMED expansion during simulated flight are needed to develop better guidelines.
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Aviat Space Envir Md · Feb 2009
Review Comparative StudyCivil aviation rules on crew flight time, flight duty, and rest: comparison of 10 ICAO member states.
Members of the International Civil Aviation Organization (ICAO) use various criteria to control flight crew scheduling and rest periods with the intention of reducing fatigue and thus improving airline safety. Comparison of these rules across nations may allow future harmonization of the criteria. ⋯ Although the 10 states in this study have common aims and premises for regulating crew duty, their regulations diverge with respect to details, using different tools in an effort to prevent the occurrence of excessive fatigue in aircrew members.
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The adverse effects of hypoxic hypoxia include acute mountain sickness (AMS), high altitude pulmonary edema, and high altitude cerebral edema. It has long been assumed that those manifestations are directly related to reduction in the inspired partial pressure of oxygen (P(I)O2). This assumption underlies the equivalent air altitude (EAA) model, which holds that combinations of barometric pressure (P(B)) and inspired fraction of O2 (F(I)O2) that produce the same P(I)O2 will result in identical physiological responses. ⋯ These data provide evidence for an independent effect of P(B) on hypoxia and AMS, and thereby invalidate EAA as an ideal model of isohypoxia. Refinement of the EAA model is needed, in particular for applications to high altitude where supplemental O2 is inadequate to prevent hypoxic hypoxia. Adjustment through probabilistic statistical modeling to match the current limited experimental observations is one approach to a better isohypoxic model.
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The adverse physiological effects of flight, caused by ascent to altitude and its associated reduction in barometric pressure, have been known since the first manned balloon flights in the 19th century. It soon became apparent that the way to protect the occupant of an aircraft from the effects of ascent to altitude was to enclose either the individual, or the cabin, in a sealed or pressurized environment. ⋯ More recent research findings on the physiological and psycho-physiological effects of mild hypoxia have provided cause for renewed discussion of the "acceptability" of a maximum cabin cruise altitude of 8000 ft; however, we did not find sufficient scientific data to recommend a change in the cabin altitude of transport category aircraft. The Aerospace Medical Association (AsMA) should support further research to evaluate the safety, performance and comfort of occupants at altitudes between 5000 and 10,000 ft.